Synthesis and characterization of cobalt ferrocyanides loaded on organic anion exchanger

Transition metal ferrocyanides have important applications in the selective removal of radioactive caesium from low level and intermediate level radioactive liquid waste streams. The microcrystalline nature of these materials renders them useless for application in column mode operations. Special preparation procedures have been developed to prepare granular solids by in situ precipitation of metal ferrocyanides on organic anion exchangers, which is suitable for column mode operations. The elemental compositions of the metal ferrocyanides precipitated inside the pores of anion exchanger were determined by analysing the dissolved samples using ICP-AES system and flame photometer. From the XRD and EDX analyses and the elemental composition of the synthesized materials, the nature of the compound formed inside the anion exchanger was found to be cobalt ferrocyanide. From SEM analysis of the samples, the particle size of the cobalt ferrocyanide precipitated inside the anion exchanger was found to be much less than that of cobalt ferrocyanide precipitated outside. The efficiency of these materials for removal of Cs was evaluated by measuring the distribution coefficient (Kd), ion exchange capacity and kinetics of Cs uptake. The Kd of the materials loaded on anion exchanger was found to be of the order of 10⁵ ml/g. The Cs uptake kinetics of the materials loaded on anion exchanger was slower than that of precipitated materials. The ion exchange capacity of the cobalt ferrocyanide loaded on anion exchanger was found to be much higher than that of the precipitated cobalt ferrocyanide.     

Direct Assessments of the Processing Time Hypothesis for the Missing-Letter Effect.

When participants search for a target letter while reading, they make more omissions if the target letter is embedded in frequently used words or in the most frequent meaning of a polysemic word. According to the processing time hypothesis, this occurs because familiar words and meanings are identified faster, leaving less time for letter identification. Contrary to the predictions of the processing time hypothesis, with a rapid serial visual presentation procedure, participants were slower at detecting target letters for more frequent words or the most frequent meaning of a word (Experiments 1 and 2) or at detecting the word itself instead of a target letter (Experiment 3). In Experiments 4 and 5, participants self-initiated the presentation of each word, and the same pattern of results was observed as in Experiments 1 and 3. Positive correlations were also found between omission rate and response latencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do noncontingent vouchers increase drug use?

Data from 2 contingency management trials, targeting opiate or cocaine use, were used to investigate whether noncontingent vouchers inadvertently reinforce drug use. The control group in each trial received noncontingent vouchers matched in value and frequency to those received by experimental groups, but independent of urinalysis. Vouchers were offered thrice weekly for 8 weeks (opiates) or 12 weeks (cocaine). Both dose-response and temporal associations of noncontingent voucher receipt with drug-positive urines were assessed. Drug use was unrelated to frequency of noncontingent voucher delivery and noncontingent voucher receipt when being drug positive was unassociated with risk of subsequent drug use, with one exception: cocaine use in the cocaine study (relative risk = 1.05, 95% confidence interval: 1.01-1.09). Overall, results do not indicate a causal relationship between noncontingent voucher receipt and increased drug use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Minimal schedulability interval for real-time systems of periodic tasks with offsets

We consider real-time systems in highly safety context where tasks have to meet strict deadlines. Tasks are periodic, may have offsets, share critical resources and be precedence constrained. Off-line scheduling should be of great help for such systems, but methods proposed in the literature cannot deal with them. Our aim is to extend and improve the well-known cyclicity result of Leung and Merill to every scheduling algorithm and to systems of interacting tasks with offsets. One of the main benefit of our result is to enable the use of off-line scheduling methods for those real-time critical systems.     

CONTRIBUTIONS TO EVOLUTIONARY SPECTRAL THEORY

Abstract. The purpose of this paper is to discuss several fundamental issues in the theory of time-dependent spectra for univariate and multivariate non-stationary processes. The general framework is provided by Priestley's evolutionary spectral theory which is based on a family of stochastic integral representations. A particular spectral density function can be obtained from the Wold—Cramér decomposition, as illustrated by several examples. It is shown why the coherence is time invariant in the evolutionary theory and how the theory can be generalized so that the coherence becomes time dependent. Statistical estimation of the spectrum is also considered. An improved upper bound for the bias due to non-stationarity is obtained which does not rely on the characteristic width of the process. The results obtained in the paper are illustrated using time series simulated from an evolving bivariate autoregressive moving-average process of order (1, 1) with a highly time-varying coherence.     

Stabilization of plutonium nano-colloids by epitaxial distortion on mineral surfaces

The subsurface migration of Pu may be enhanced by the presence of colloidal forms of Pu. Therefore, complete evaluation of the risk posed by subsurface Pu contamination needs to include a detailed physical/chemical understanding of Pu colloid formation and interactions of Pu colloids with environmentally relevant solid phases. Transmission electron microscopy (TEM) was used to characterize Pu nanocolloids and interactions of Pu nanocolloids with goethite and quartz. We report that intrinsic Pu nanocolloids generated in the absence of goethite or quartz were 2-5 nm in diameter, and both electron diffraction analysis and HRTEM confirm the expected Fm3m space group with the fcc, PuO2 structure. Plutonium nanocolloids formed on goethite have undergone a lattice distortion relative to the ideal fluorite-type structure, fcc, PuO2, resulting in the formation of a bcc, Pu4O7 structure. This structural distortion results from an epitaxial growth of the plutonium colloid on goethite, leading to stronger binding of plutonium to goethite compared with other minerals such as quartz, where the distortion was not observed. This finding provides new insight for understanding how molecular-scale behavior at the mineral-water interface may facilitate transport of plutonium at the field scale.     

Attention soutenue et motivation : une approche chronopsychologique.

Discusses the effects of motivation on ability to sustain attention. We emphasize the fact that motivation should be considered a masking factor in ultradian rhythmicities of cognitive efficiency. In the first part of this article, several studies are listed. These studies attempted to show behavioral fluctuations when sustained attention is required. The inconsistency of the results brought forth by such studies is pointed out. In the second part of the article, the question of the status granted to motivation in chronopsychological studies, where motivation is manipulated in several ways, is discussed. Interpretations are revisited in terms of intrinsic and/or extrinsic motivation concepts. Some of these chronopsychological studies used only extrinsic motivation whereas others created conditions in which intrinsic motivation was favoured (for example, knowledge of results, which appears to be a prominent masking factor). Finally, we propose several hypotheses in order to support the assumption of a stabilizing effect provided by intrinsic motivation. We conclude by insisting upon the necessity of involving participants in tasks requiring complex cognitive activity, which contrasts with the monotonous and too simple tasks used frequently in chronopsychological studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Variability and molecular typing of Streptococcus thermophilus strains displaying different proteolytic and acidifying properties

Proteolytic and acidifying properties of Streptococcus thermophilus strains isolated from yoghurt or cheeses were evaluated. Among 30 strains tested, 12 exhibited cell envelope-associated proteinase activity (PrtS⁺), three displayed a slight PrtS activity (PrtS^+/?) and 15 were PrtS^?, despite the presence of the corresponding gene (prtS) in eight of them. Sequencing of the prtS gene in four PrtS^? and one PrtS⁺ strains revealed that the absence of PrtS activity in the PrtS^? strain probably results from an alteration of the prtS regulation. The strains displaying the highest acidifying capacities were all PrtS⁺. All but one PrtS⁺ strains were phylogenetically close, as shown by the sequencing of their rDNA internal transcribed spacer (ITS) 16S-23S. More specifically, the high proteolytic and acidifying capacities are associated with the presence of a type II-ITS.     

Differential sensitization, retention, and generalization of habituation in two response systems in the blowfly (Calliphora vomitoira).

Conducted 3 experiments with 95 blowflies to elicit a cardiac disturbance and a motor response by the same moving visual stimulus. In Exp I, the habituation of these responses developed at an equal rate during stimulus repetition. After a rest period, whereas habituation of motor responses was completely retained, a substantial recovery of cardiac responses was observed. The use of distributed trials in Exp II helped to dissociate the influence of sensitization and habituation processes on the behavioral outcome. Habituation of motor responses, in addition to a longer retention, appeared to be more easily generalized after a spatial displacement of the stimulus in Exp III. Data support the hypothesis that habituation processes develop independently in different response systems, even if they have the same sensory input. The faster reversibility of habituation of cardiac responses is discussed, with reference to a preparatory function for locomotor behavior. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive—behavioral treatment of obsessive thoughts: A controlled study.

Twenty-nine patients with obsessive-compulsive disorder as diagnosed in accordance with the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised; American Psychiatric Association, 1987) who did not have overt compulsive rituals were randomly assigned to treatment and waiting-list conditions. Patients in the treatment condition received cognitive-behavioral therapy consisting of a detailed explanation of the occurrence and maintenance of obsessive thoughts, exposure to obsessive thoughts, response prevention of all neutralizing strategies, cognitive restructuring, and relapse prevention. Compared with waiting-list patients, treated patients improved significantly on measures of severity of obsessions, current functioning, self-report obsessive-compulsive symptoms, and anxiety. When waiting-list patients were subsequently treated, the combined group improved on all outcome measures. Treatment gains were maintained at 6-month follow-up. Results indicate that cognitive-behavioral therapy is effective in the treatment of patients with obsessive thoughts, a group that has often been considered resistant to treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)